Weight and balance?

[pd2]

Thought I would come out of my cubby hole in Rotorheads and check out the other forums. I love this forum.

Although not about a passenger, rather a cabin crew.

Aircraft less than half full. Me sitting over wing in an aisle seat, vacant middle seat and a person at the window.

Just before take off, a female cabin crew approaches me and states

"I am sorry sir, but due to weight and balance reasons, you will need to move three rows back"

What the is this about... seriously. If an 80kg person moving 3 metres is so critical to the W&B of a 400+ton aircraft, then we are all in trouble. Hopefully no-one leaves their seat during the flight.

Unfortunately, the request was so stupid, that I politely refused, told her I was comfortable where I was and asked her to explain her why.

Just a thought.... if you treat passengers like idiots... they might just take offence and become uncooperative.

Could someone shed some light on this ridiculous request. Is it used often for some reason? Why would the request be made... keeping in mind the aircraft was less than half full... and CC are not Load Controllers.

PD2

[MathFox]

Balance is relevant, even for the bigger jets: Tail strike during take-off, Boeing 737-800, Rotterdam Airport - De Onderzoeksraad voor veiligheid

(I admit that the above example was more than three rows for a single passenger...)

[pd2]

Thanks Mathfox, but I fail to see the relevance of this article. Tail strike could occur for any number of reasons - poor pilot skills, aircraft empty causing over-rotating if the pilot has received no training for empty aircraft flight, tail heavy loading...

Of course I understand loading is an issue... as it is with almost every single aircraft ever built. These can be some pretty complicated calculations... so I don't believe a CC can calcuate the loading off the top of her head without even knowing what is loaded in the cargo hold, the Basic empty weight, moment arms etc...

[Flightfreak]

There could have been all sorts of reasons.

Cc might have wanted to move you closer to the rest of the passengers to make their work easier. Would make cleaning after the flight easier, etc...

Your position on the airplane might not per see be a mass and balance problem but could have been not in line with the loading calculations performed. For that reason CC could have been instructed to move 'everyone' according to some last minute m&b change performed calculations.

Did you eventually move?

[davecfm56]

pd2, as flightdeck we tell the cabin crew where to seat passengers in order place the aircraft cofg in the required position for take off. its important to have the actual cofg as close to the calculated one for take off for setting the stab trim for the rotation. once airborne you're free to move around the aircraft as we 'feel' trim changes and correct as required. our load sheets are designed in such a way that we split the cabin into sections or bays. of course the aircraft would fly if one or two passengers weren't in the required bay but its a legality issue. the loading of the aircraft MUST reflect the load sheet.

the check in staff often wont know if the aircraft is carrying cargo or the weight distribution in the holds (which often arrives at the aircraft first and therefore is loaded much earlier than the passengers). so will allocate seats in a standard fashion. once we're passed the passenger figures and complete the load sheet we may find that the passenger distribution is incompatible with the hold weight distribution. its much easier to ask a passenger to move than it is to move bags or cargo.

[MathFox]

pd2, I'll give you the gist of the accident report: The plane was so aft-loaded with passengers that the tail struck the ground during the take-off roll, far before V1 or VR were reached. The pilots aborted the take off uneventfully; the plane needed some repairs before being brought back into service.

[jetset lady]

pd2,

As has already been explained in detail by davecfm56, the CC do not calculate the loading. The message is passed to us from the Flight Crew having usually come, I think, from Flight Ops. Anyway, aside from the legal angle, is it really worth taking the risk no matter how small it may seem, just for the sake of sitting in a particular seat for take-off? I'll happily admit that I'm no expert on the intricacies of weight and balance, so I'll trust those that are. If they say someone needs to be moved, then moved they shall be! Whether that be to their new seat or off the aircraft is up to them.

Unfortunately, the request was so stupid, that I politely refused, told her I was comfortable where I was and asked her to explain her why.

Just a thought.... if you treat passengers like idiots... they might just take offence and become uncooperative.

Just out of interest, if the Captain had personally approached you in the cabin and asked you to move seats for weight and balance issues, would you have assumed he/she was treating you like an idiot and replied that you were quite comfortable where you were, thank you. Or was it just because it was a CC member that asked you to move? After all, what could she possibly know about such complicated technicalities?

Still, at least you can now be assured that you weren't being treated like an idiot.....

[TightSlot]

It's as well that you didn't meet me instead pd2 - You would have moved: Either the three rows back or back up the jetway to the terminal.

Weight & Balance (Trim) are not relevant once airborne - the aircraft trims itself in flight. However, for take-off especially, trim is important. Therefore. if moved, you can then move back after take-off safely.

You are entitled to an explanation, and courtesy - and then the entitlement thing stops and you are required to comply. Your 'comfort' or seat preference are factors, and ones that a good crew will manage appropriately - but they are irrelevant when given a clear instruction by a crew member, acting with the delegated responsibility of the Captain (as they are). I'm afraid this one isn't up for discussion.

[Juan Tugoh]

Weight & Balance (Trim) are not relevant once airborne

I seriously hope you do not really believe that. Aircraft trim and balance are relevant through the entire flight envelope. There is no law of physics that mysteriously disappears when an aircraft takes off. The same system used to trim the aircraft in flight is used by the pilots to trim the aircraft for takeoff. A trim system is used to relieve control loading, that loading may be held by brute force but is tiring. There is a point at which no amount of brute force (or a trim system) can hold enough control deflection to allow safe flight. In flight the pilots (or autopilot) will use this trim system to maintain light control loading, but the laws of physics will dictate when stability is lost.

If you were to load most modern jet aircraft with passengers and freight only at the rear of the aircraft and none at the front, they would not fly safely - they would be out of trim. This would not change magically if you could somehow take-off.

You are entitled to an explanation, and courtesy - and then the entitlement thing stops and you are required to comply. Your 'comfort' or seat preference are factors, and ones that a good crew will manage appropriately - but they are irrelevant when given a clear instruction by a crew member, acting with the delegated responsibility of the Captain (as they are). I'm afraid this one isn't up for discussion.

This is on the money, if issued an instruction regarding the safety of the flight by the crew, failure to comply is a criminal act under the ANO. Crew do use the old trim argument to move people as it is easier to baffle people with a 'spurious' technical reason than tell them its for reasons of exit coverage etc.

[Geoff44]

On most aircraft passengers sitting over the wing have no impact on the balance of the aircraft. I suspect you were asked to be moved for a different reason and the cabin crew just used weight and balance as an excuse

[antonovman]

"On most aircraft passengers sitting over the wing have no impact on the balance of the aircraft. I suspect you were asked to be moved for a different reason and the cabin crew just used weight and balance as an excuse"
Well that is more or less correct but it depends on the size of the a/c. If we are talking about a 20 seater a/c one pax will make a difference, however on a large wide body, moving just 1 pax is a drop in ocean

[pd2]

Aircraft was 737

I should have also mentioned that I was the only person that was asked to move and, it seemed to me, to be a spur of the moment decision. Casually walking down the aisle checking seat belts. Takes a step past my seat then returns. I would have thought that an instruction from the Captain would have seen her act with more purpose. Of course this is only my perception... Maybe she should have moved someone from the extremities of the aircraft to have a greater effect.


What you all seem to be missing is that I was overwing... pretty much the pivot point and CofG point of the aircraft. To move me three rows would have achieved next to nothing. If I was in Row 1 and asked to move to Row 26... well yes I can understand that.

Mathfox... Thank you for explaining the relevance of that article. With only 4 lines of text in the article, it was difficult to understand the cause of the strike.

davecfm56... Thanks for the explanation. Not sure what aircraft you fly, but on the 737, it is actually quite difficult to throw the aircraft out of balance unless you decide to seat 350 passengers in the back 15 rows, or the load controller decides to load all the freight at one end of the aircraft.

Jetset Lady... Yes, if the Captain had personally approached me, then I would have moved at his request. Please don't imply that I dislike CC or believe them inferior... and I am not one of your typical difficult passengers. I tend to be the passenger that just reads a book for the entire flight, but the obvious deception really irked me!

Flightfreak... No, I didn't move. The CC just moved on and continued checking seat belts. Hard to believe this was an instruction from the flight deck.

Tightslot... Ditto Juan Tugoh

Antonovman... Thank you. Someone finally sees my point.

About me... ATPL Captain, with 18years experience working in Helicopter Offshore operations... so, yes, I understand the legalities of W&B, Manifests and the complexities of CofG calculations... which is why I find it so difficult to accept any of your explanations as... and I will say it again... I was overwing and asked to move three rows. So I doubt this was a request from the flight deck as moving one person 3 metres would have achieved next to nothing.

Anyway, on a lighter note, thanks for your contributions and please don't take my posts as arrogant. Just being curious. I was actually hoping to hear that this comment is used sometimes for xxxx reason or yyyyy reason which is what Juan Tugoh alluded to. Thats it from me... I'll go back to Rotorheads.

[Matt101]

I'm a fairly new fATPL holder but was previously Crew.

In my honest opinion, I have seen the Pax Info List have some odd choices of seat closure. Often you will see a seat blocked for take off that was open on a previous sector with the assumption usually being it is a M&B issue though that may be an incorrect assumption on occasion.

However CC are not generally trained in the why's and where for's of load control and their choice of seat allocation, we were simply asked to enforce it. That is made all the more difficult when pax do not comply.

At LGW I found myself on a 737 one day asking a gentleman to move seats to the one he was allocated (about a 10 row change from over the exit to the near aft row), he refused stating he was a TRI for another 737 operator and that I was being difficult. Thankfully my flight crew came out and moved said gentleman.

Was the M&B out with him out of place? honestly not having gotten further than CRM in my company type & line training yet I really am not sure, I've seen people moved from first class to last row before but this is a far more obvious choice than on a stubby 73. However At the time I was doing my job as trained, as was the young lady on your flight.

There is of course every chance she was misinformed or feeding you a line for whatever other reason, however, like the above TRI your place is not to judge but to comply with the polite request and, if you feel hard done by, speak to the Senior after take off about moving back.

Not having a go but we get enough of a hard time from those entirely ignorant of aircraft, airlines and aviation, when a fellow cloud dweller is aboard it is nice to feel you are on the same team at least.... now I best not rant about the positioning Delta girl who insisted her seat was upright and why had I woken her for landing - she was in a flat bed....

[Diplome]

pd2:

The reasoning as to why you were asked to move isn't the most interesting item in your post, its that you were requested to move by a Cabin Crew member AND REFUSED??

Understand that I'm not a defender of Cabin Crew at all costs. In fact, I've been tad disgusted reading Cabin Crew members defend the absolutely abusive and dangerous behavior of the nitwit from JetBlue

That being said, when you step onto that aircraft there is a food chain...and you're not at the top of it.

If you have a problem do what a reasonable individual would do...follow the order and then write to the Company for clarification. There are security reasons that may have been the source of the Cabin Crew's request (my husband has been on the receiving end of one of those..the Crew simply quietly moved some individuals to new seats...a few minutes later security arrived to remove an individual from the plane).

To simply say "No", never correct.

[TightSlot]

Hmmm

Well let's try some more and see where it goes.

Juan Tugoh - Thanks for the explanation on trim, the process of which I understand at a basic level. I had simplified my explanation somewhat, since not everybody is familiar with the concepts discussed (or is interested). The fact remains that once the aircraft is airborne it is in trim assuming no sudden mass movement of payload and it continues to trim itself as the payload wanders around the aircraft looking for another cocktail or a pee. If you were to load a modern aircraft in the manner you describe, its' performance once airborne would be somewhat academic, since it would never become so.

Geoff44 - Possibly, but beyond your own experience of trimming an aircraft, you don't know that for fact, and should possibly be more careful when presenting an educated guess as such. Had you, in fact, been responsible for producing the loadsheet for that aircraft, how would you have felt, on producing a solution to bring the aircraft back in trim (i.e. moving some mass from one area to another), only to be told that the mass involved didn't feel like moving? I suspect that your reaction might be rather closer to mine under those circumstances?

FYI - 737-800 are especially prone to trim issues (long, thin) when loads are low. This can be exacerbated by the hold loading procedures adopted by LoCo fast t/round carriers.

pd2 - None of what you say is 'wrong' however in my view, it is a distraction. You'll be able to discuss w/b issues in one of the various tech forums on PPRuNe, where some of the answers that you receive may surprise you slightly. However, since this was raised in the Cabin Crew forum, we should discuss it from a CC point of view. From a CC perspective, it is a concern that given your experience as ATPL and Captain, you should feel comfortable with your actions in this particular instance. I regard it as inappropriate that you should have acted upon a request from an FA as if you were a part of the operating crew, when in fact your role was quite different. I don't believe that you would be happy for pax on a flight of which you were the Commander to disregard an instruction from your crew acting with your delegated authority, citing prior knowledge of the theory of flight: Had you been asked to leave the flight deck to explain your reasoning to a reluctant to a move customer, you might well find that some shortness in your tone and language developed. It is unclear from your posts whether you were travelling on an industry ticket or a commercial basis.

There is clearly a possibility that the CC in this instance was playing games to make service or other issues easier: I hope not, because that kind of behaviour discredits us all, and, as demonstrated by the existence of this thread, makes it more difficult for the rest of us to do our jobs as required, in the future, when necessary. The point is that none of us know for sure if this was the case, and for the purposes of discussion, we should treat it as being a serious request.

Diplome - Quite so!

[paddy_22002]

Hi PD2,

the 737 isn't a 400T+ aircraft. On the larger aircraft the weight and balance (loadsheet) is usually made using standard weights and the aircraft divided into compartments. The weight (cargo and/or pax) is distributed so the the aircraft centre of gravity remains within limits.
On the smaller aircraft such as the 737/airbus it may be that the C of G is on a limit and as such blocking out or moving a single row of seats/pax will bring it back within limits. I have never seen a single pax moved to comply with limitations although I have removed a galley bar (about 90Kgs) to get a 737 below Max take off weight. Not quite the same thing but helps illustrate how critical weights can be. I know some operators will only load hold luggage in a single compartment ( allows a quicker turnround and less staff) and hence trim the aircraft by moving the other variable load(pax).
C of G can also be critical in-flight especially if the fuel in an aft tank fails to be burnt (744).
From the information I'm unsure in your example if it was a requirement for that flight. If it was either you should have been moved or off-loaded.

[pd2]

Paddy_22002... You are correct. It is not a 400+ton aircraft. 79ton would be closer to the mark. Oops.

[john_tullamarine]

Several interesting points in this thread. Some comments with my weight control officer chappie's hat on ... (and others already have made several of these)

Unfortunately, the request was so stupid, that I politely refused, told her I was comfortable where I was and asked her to explain her why.

Not necessarily stupid - it really depends on the aircraft, what sort of loading system the operator uses, LMC considerations, and where the initial loading position is in the envelope.

Probably better to not refuse the request (direction) as it would have had the commander's authority behind it, either implicit or explicit - certainly OK to query the reasoning in an appropriate way for whatever interest you may have had either at the time or, more usefully, later during the flight.

I don't believe a CC can calcuate the loading off the top of her head

Most unlikely that this was the case. Either the CC was applying prescribed loading rules or acting at the direction of the flightdeck folk. Mind you there is no reason why CC can't be highly expert in weight control matters - I've flown with some very switched on CC folk over the years.

its important to have the actual cofg as close to the calculated one for take off for setting the stab trim for the rotation

Not really - two options. Either rework the load to achieve the paperwork or, often a lot simpler if the final load is different, use the company prescribed protocol to record that different and refigure the numbers (usually by LMC protocols or redoing the sheet). Looking up a revised stab trim setting is not in the league of brain surgery and usually takes all of a couple of seconds.

once airborne you're free to move around the aircraft as we 'feel' trim changes and correct as required

That only goes so far. In some/many/most jurisdictions the operation is required to be constrained to keep the CG within the envelope throughout flight. It's not at all difficult to have folk wandering about the cabin and end up with the CG too far one way or another. Especially if the CG ambles too far aft, things can go from bad to worse fairly quickly.

our load sheets are designed in such a way that we split the cabin into sections or bays.

Typical approach but it should be noted that it reduces flexibility (and accuracy) while increasing ease of execution, management and general convenience.

the aircraft would fly if one or two passengers weren't in the required bay

A big difference between flying and flying while still being in the approved envelope. If the load sheet has had an appropriate error analysis it should have enough good guidance to provide for small misloadings. However, some don't and, if you move the load (even a passenger or two) while being near the limits, you could very easily find yourself outside the envelope requirements

loading of the aircraft MUST reflect the load sheet.

.. or you redo the load sheet for the revised load or do whatever other procedure is prescribed by the company to account for changed loading. Certainly should not be a necessary case of "having" to bust yourself to rearrange things to achieve an earlier load sheet iteration.

its much easier to ask a passenger to move than it is to move bags or cargo.

Exactly.

I suspect you were asked to be moved for a different reason and the cabin crew just used weight and balance as an excuse

It may well have been. Equally, it may have been so simple a case as that operator's loading system's being seat prescriptive - ie the CC noted that the passenger was not in the assigned seat and was only requesting that the assigned seat be used.

[TurningFinals]

The aircraft cabin will be split into bays, it's highly likely the CC was asked to move one pax from bay Y to bay Z by the captain.

In a 737 i can't imagine one passenger moving between two neighbouring bays making a huge difference, but as has been mentioned, the bay split/cargo split must be as per the paperwork.

Personally, I think it's incredibly rude (especially as an aviatior yourself) to refuse a request such as this from CC.

[bunnygirl]

Firstly pd2, you say you were at the overwings, was the seat you had, the one listed on your boarding pass, or had you moved there because you could see the flight wasnt busy?

I recently had a very similar incident to that that pd2 described, coming out of LUX on the 737-400. The gentleman in question acted in exactly the same manner as pd2! Don't think it was you though!

At BA we are given a list of blocked seats just before the doors are closed, and as has been explained before, these seats should nt be occupied for take off or landing! The weight and balance of the aircraft is finally calculated once the 'flight has closed'. Which is why you hear of passengers who have virtually no knowledge of aviation complaining when they are denied boarding, and stating they were only 4 mins late from checkin closing!

This calculation process starts then!! And the blocking of seats begins, when it is a light load! On this particular flight I operated, we even had ballast of sacks of sand in the hold to maintain the crucial weight and trim of the aircraft!

I was once told that we have this particular problem at BA rather than any other operator of the B 737-400, as we only have a max of 147 seats fitted as opposed to some who have 172!! How true that is I don't know, maybe one of my BA flight Crew boys or girls can confirm or deny!

As for pd2.. Look at it another way, if it wasn't a problem for you to stay where you were do you think we d have let you stay there... YES, we would. As cabin crew these days, we get so many amateur pilots who think they know best, and can be quite vocal in their distain for our role sometimes, that we really don't go out of our way to pee you off you know!!

Still say each gate area should show a short video on a loop " Fundamentals of Flying", to explain simple things like why we do a demo.. Etc etc!,

But hey what do I know.. I'm just a simple hosti!